New Arecibo radar data has allowed better calculations of the trajectory of Apophis. Cumulative probability of impact (from JPL NEOPO Sentry Assessment) changed from 1.6e-04 (on 14 April 2006) to 4.4e-05 (on 18 May 2006). I have quoted multiple sections from a recent article below:
The chances of collision with the asteroid Apophis in 2036 now stand at 1 in 24,000, said Steve Chesley, an expert on near-Earth objects at NASA's Jet Propulsion Laboratory. That's a significant advance from the previous orbital predictions, which set the odds of impact at 1 out of about 6,000.
The May 6-7 window for radar observations represented the best opportunity until the end of 2012. Jon Giorgini, a senior analyst for the Solar Systems Dynamics Group at JPL, said the Arecibo team got a good fix on Apophis. "We were able to improve our understanding of its motion by about 6 millimeters per second," Giorgini.
Previously, NASA had said that no more observations could be made until 2013. But on Thursday, Chesley said more may be known before then. "Actually, we're going to probably get some observations, though they'll be difficult to obtain — maybe by next spring," he said. Astronomers at the Mauna Kea Observatory in Hawaii could spot the asteroid in 2007 as well as in 2011, he said.
In the 2012-2013 time frame, Arecibo could come into play again. Giorgini said those observations would be even more accurate because Apophis would come within 8.3 million miles (13 million kilometers) of Earth — much closer than this month's pass at a distance of 26 million miles (42 million kilometers).
"Asteroid risk to Earth lowered, scientists say: Chances of impact move ‘in right direction,’ toward odds of 1-in-24,000"
Alan Boyle
Science editor
MSNBC
18 May 2006
Link: MSNBC Article
"99942 Apophis No Longer a Threat for 2036"
18 May 2006
Link: About.com
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